Reversible colorless-cyan photochromism in Eu²⁺-doped Sr₃YNa(PO₄)₃F powders

Abstract

Photochromic materials have attracted increasing interests as optical switchers and erasable optical memory media. Here, we report on a novel reversible colorless-cyan photochromic powder material Sr3YNa(PO4)3F:Eu 2+ . The photochromic properties including coloring and bleaching are characterized by reflectance spectra after the powder is irradiated by different wavelength light for different irradiation times or thermal treatment. The results turn out that it can be colored by short wavelength light (200-320 nm) and bleached by longer wavelength light (320-800 nm) or thermal treatment at 240 °C. The optimal doping concentration of Eu 2+ is determined to be about 0.5 mol%. It shows high fatigue resistance in photochromism performance. Electrons in 4f ground levels excited by short wavelength irradiation to higher 5d states of Eu 2+ and then captured by traps are responsible for the coloring process. Correspondingly, the releasing of trapped electrons from two kinds of traps with different depths causes the initially fast and later slow bleaching processes. The critical role of charge carrier motions between two different traps is discussed. The colorless-cyan photochromism can be explained semi-quantitatively on the basis of obtained results. A tentative model was proposed to illustrate the PC mechanism.

Reversible Upconversion Luminescence Modification Based on Photochromism in BaMgSiO4:Yb3+,Tb3+ Ceramics for Anti‐Counterfeiting Applications

“…Excellent reversible photochromism between the gray and pink colors of the BMS:Yb,Tb ceramic were obtained after sixth cycles of alternating between 254 nm light irradiation and thermal stimulation at 125 °C for 10 min. In contrast to previous works, thermal stimulation–induced bleaching was realized at a lower temperature in the present work, which is advantageous for the practical application of the BMS:Yb,Tb ceramic …”

“…Very recently, entirely photostimulation‐induced reversible modulation of downshifted photoluminescence was obtained in Sr 2 SnO 4 :Eu 3+ . However, in previous investigations, the luminescence spectra of rare earth ion‐doped photochromic phosphors can overlap with their excitation spectra, reducing the ability of detecting the luminescence . Upconversion luminescence (UCL) phosphors doped with rare earth ions can convert two or more photons with low energy into one photon of higher energy.…”

Reversible multiplexing for optical information recording, erasing, and reading-out in photochromic BaMgSiO4:Bi3+ luminescence ceramics

“…To improve the storage capacity, multiplexing the information storage is required [9][10][11][12]. Photochromism is always accompanied by the reversible change of chemical substances between two states upon light stimulation, which can switch the absorption property of materials [13][14][15][16][17][18][19][20]. The "0" or "1" digital code can be represented by each state, corresponding to "off" or "on" states.…”

Photoluminescence and Scintillation Modulation Upon UV/X‐ray‐Induced Photochromism in Europium Tungstate Phosphors

“…However, most of the materials only exhibit X‐ray‐induced photochromism below room temperature, which increases cost and make it difficult for use . Moreover, they are mainly based on organic compounds,, which have some intrinsic shortcomings such as low thermal and chemical stability and environmentally hazardous synthesis procedures, limiting their practical applications . In this context, the development of inorganic photochromic compounds has received considerable attention due to their high thermal and chemical stability, controllable macroscopic shape molding and mechanical strength in comparison to the organic counterparts ,.…”

“…‐ These unique features may be useful in the understanding of eventual structural modifications arising from X‐ray irradiation processes. Although the development of inorganic materials that combine photochromic and luminescent properties have been increased in the last years due to their potential application in photonic devices,,,‐ only few of them show luminescence modulation upon photochromism. The luminescence photoswitching opens new possibilities for the developing non‐destructive optical readout systems and quick‐responsive sensors ,,,,.…”